Calcium (kí hiệu là Ca) là một loại khoáng chất có vai trò rất quan trọng trong cơ thể người. Trong cơ thể, calcium chiếm 1,5 – 2% trọng lượng, 99% lượng calcium tồn tại trong xương, răng, móng và 1% trong máu. Calcium kết hợp với phosphorus là thành phần cấu tạo cơ bản của xương và răng, làm cho xương và răng chắc khỏe. Khối lượng riêng của calcium kim loại là 1,55 g/cm³. Giả thiết rằng, trong tinh thể calcium, các nguyên tử là những hình cầu chiếm 74% thể tích tinh thể, phần còn lại là khe rỗng. Cho nguyên tử khối của calcium là 40 amu. Bán kính nguyên tử calcium là

Tất cả những gì đã diễn ra trong quá khứ, tồn tại một cách khách quan, không phụ thuộc vào ý muốn chủ quan của con người được gọi là:

Read the passage carefully. Choose an option (A, B, C or D) that best answers each question from 23 to 30.

1. How do children learn about wildlife? And is what they learn the sort of thing they should be learning? It is my belief that children should not just be acquiring knowledge of animals but also developing attitudes and feelings towards them based on exposure to the real lives of animals in their natural habitats. But is this happening?

2. Some research in this area indicates that it is not. Learning about animals in school is often completely disconnected from the real lives of real animals, with the result that children often end up with little or no understanding or lasting knowledge of them. They learn factual information about animals, aimed at enabling them to identify them and have various abstract ideas about them, but that is the extent of their learning. Children's storybooks tend to personify animals as characters rather than teach about them.

3. For direct contact with wild and international animals, the only opportunity most children have is visiting a zoo. The educational benefit of this for children is often given as the main reason for doing it but research has shown that zoo visits seldom add to children's knowledge of animals – the animals are simply like exhibits in a museum that the children look at without engaging with them as living creatures. Children who belong to wildlife or environmental organizations or who watch wildlife TV programmes, however, show significantly higher knowledge than any other group of children studied in research. The studies show that if children learn about animals in their natural habitats, particularly through wildlife-based activities, they know more about them than they do as a result of visiting zoos or learning about them in the classroom.

4. Research has also been done into the attitudes of children towards animals. It shows that in general terms, children form strong attachments to individual animals, usually their pets, but do not have strong feelings for animals in general. This attitude is the norm regardless of the amount or kind of learning about animals they have at school. However, those children who watch television wildlife programs show an interest in and affection for wildlife in its natural environment, and their regard for animals in general is higher.

What can be inferred from paragraph 4 about children's attitudes to animals?

Để nghiên cứu sự sinh trưởng và phát triển của thực vật, người ta tiến hành một thí nghiệm như sau:

- Cây mầm 1: chiếu sáng từ một phía lên bao lá mầm.

- Cây mầm 2: cắt bỏ đỉnh ngọn, rồi chiếu sáng từ một phía

- Cây mầm 3: che tối phần bao lá mầm, chiếu sáng từ một phía.

Nhận định nào sau đây không chính xác?

Bất phương trình nào sau đây là bất phương trình bậc nhất hai ẩn?

Read the following passage about Singapore Science Centre and mark the letter A, B, C, or D on your answer sheet to indicate the best answer to each of the following questions from 23 to 30.

The Singapore Science Centre, situated on a sprawling six-hectare site in Jurong, offers a captivating way to explore the wonders of science and technology. Here, visitors can engage with interactive exhibits that make learning both fun and memorable. Clap your hands, and colorful bulbs will light up; spin a wheel, and it will activate a fan. This engaging environment sparks curiosity and fuels the imagination of both children and adults.

The centre boasts more than four hundred exhibits across various fascinating topics, including solar radiation, communication, electronics, mathematics, nuclear energy, and evolution. These exhibits are designed to foster interest in science and technology among the public, making the centre a hub for educational exploration.

Notably, it is the first science centre to be established in Southeast Asia. Officially opened in 1977, the centre now welcomes an average of 1,200 visitors daily, highlighting its enduring popularity and educational value.

The exhibits are thoughtfully arranged across four main galleries: the Lobby, Physical Sciences, Life Sciences, and Aviation. To ensure a fresh and engaging experience, the exhibits are renewed annually, encouraging repeat visits. Visitors are encouraged to interact with the exhibits, as opposed to traditional “hands-off” policies in most museums. Here, pushing buttons, turning cranks, or pedaling mechanisms are all part of the fun and learning experience.

The Discovery Centre, added in 1985, is specially designed for children aged three to twelve, providing an exciting space for young minds to explore and experiment. Most recently, a stone-age exhibit was introduced, showcasing extinct animals and early human life, offering insights into prehistoric times.

With its interactive displays and immersive environment, the Singapore Science Centre continues to inspire a love for science and discovery, making it an unforgettable destination for learners of all ages.

In which paragraph is the annual renewal of the exhibits mentioned?

Read the following advertisement and mark the letter A, B, C or D on your answer sheet to indicate the option that best fits each of the numbered blanks from 1 to 6.

MAKE MEMORIES WITH CUSTOM PHOTO BOOKS

Are you tired of digital photos sitting on your phone or computer? Turn them into beautiful custom photo books with our easy-to-use platform. Our service ___(1)___ you to upload, organize, and design your own photo book, creating a unique keepsake to treasure forever. You can ___(2)___ between different layouts, themes, and covers to make your book truly special. With our high-quality printing, your memories will ___(3)___ vibrant and long-lasting. Plus, our photo books make great gifts for family and friends. Don't ___(4)___ your memories – capture them in a book you'll love to ___(5)___ for years to come. Start designing today and ___(6)___ 20% off your first order!

Cho các phát biểu sau:

(1) Các amino acid là chất rắn ở diều kiện thường.

(2) Glycine tác dụng với ethanol có mặt HCl thu được ester có công thức \({{\text{H}}_{2}}\text{NC}{{\text{H}}_{2}}\text{COO}{{\text{C}}_{2}}{{\text{H}}_{5}}\).

(3) Ở \(\text{pH}=2\), alanine di chuyển về phía cực âm dưới tác dụng của điện trường.

(4) Cho ethylamine dư vào dung dịch \(\text{CuS}{{\text{O}}_{4}}\) thu được dung dịch có màu xanh đặc trưng.

(5) Methylamine có tính base yếu hơn ammonia.

Các phát biểu đúng là:

Đọc đoạn trích sau và trả lời câu hỏi:

Thị lẳng lặng theo hắn vào trong nhà, cái nhà vắng teo đứng rúm ró trên mảnh vườn mọc lổn nhổn những bụi cỏ dại. Thị đảo mắt nhìn xung quanh, cái ngực gầy lép nhô lên, nén một tiếng thở dài. Tràng xăm xăm bước vào trong nhà, nhấc tấm phên rách sang một bên thu dọn những niêu bát xống áo vứt bừa bộn cả trên giường dưới đất. Hắn quay lại nhìn thị cười cười:

- Không có người đàn bà, nhà cửa thế đấy!

Thị nhếch mép cười nhạt nhẽo . Tràng vỗ vỗ xuống giường đon đả:

- Ngồi đây!... Ngồi xuống đây, tự nhiên...

(Vợ nhặt, Kim Lân)

Chi tiết thị “nén một tiếng thở dài” cho thấy thái độ gì của người vợ nhặt?

Điểm bù ánh sáng là cường độ ánh sáng mà ở đó, cường độ quang hợp như thế nào?

Read the following leaflet and mark the option that best fits the numbered blanks from 19 to 24. 

TIPS FOR BETTER TIME MANAGEMENT

Want to get more done in less time? Follow these strategies for improving your productivity and focus!

Common Struggles: 

Many people (19) _____ effective time management, leading to stress and unfinished tasks. Research shows that nearly 70% of workers feel overwhelmed by their workload.

Actionable Solutions!

- Prioritize your tasks! Start by making a to-do list and (20) _____ with the most important tasks first.

- Break down big projects! Tackling a large project can be daunting, but breaking it into smaller, (21) _____ parts helps ensure progress without feeling overwhelmed.

- Avoid distractions! (22) _____ multitasking, focus on one task at a time to (23) _____ your efficiency.

- Take breaks! Give yourself regular breaks to rest and recharge, (24) _______ can help maintain a higher level of productivity.

Các quốc gia đang phát triển thường có đặc điểm gì?

Phong trào đấu tranh của công nhân Việt Nam trong những năm Chiến tranh thế giới thứ nhất đã phản ánh điều gì?

Thế nào là tỉ lệ tăng tự nhiên dân số?

Các cấp độ tổ chức sống có những đặc điểm chung nào?

Ý nào dưới đây là nói về thuế gián thu?

Các cấp tổ chức của thế giới sống không bao gồm thành phần nào?

Read the following passage about the urban shift and mark the letter A, B, C or D on your answer sheet to indicate the best answer to each of the following questions from 31 to 40. (2,5 points)

            [I] Water is one of the most essential resources on our planet, vital for all forms of life. However, increasing demand and pollution are putting immense pressure on our freshwater supplies. [II] According to recent studies, nearly 2 billion people worldwide live in countries experiencing high water stress, leading to a decline in the availability of this precious resource. This situation not only affects drinking water but also agriculture, sanitation, and energy production.

            The primary causes of water scarcity include population growth, urbanization, and climate change. As cities expand, the demand for water increases significantly. Moreover, agricultural practices that rely heavily on water are becoming unsustainable in many regions. Climate change further exacerbates these issues, causing unpredictable weather patterns and extreme droughts, which reduce water availability.

           [III] In response to this growing crisis, everyone must prioritize water conservation. Simple actions, such as fixing leaks, using water-efficient appliances, and practicing mindful consumption, can make a significant difference. Additionally, implementing policies that promote sustainable water management and investing in technologies for water recycling can help mitigate the impacts of water scarcity. [IV]

            Despite these efforts, the challenges remain substantial. It is crucial that we recognize the importance of conserving water and take immediate steps to protect this vital resource for future generations.

Which of the following best summarises paragraph 3?

Hai vật có khối lượng \({m_1} = 1kg,{m_2} = 2kg\)chuyển động với vận tốc tương ứng là \({v_1} = 3m/s,{v_2} = 2m/s\) và \(\overrightarrow {{v_1}} \)vuông góc với \(\overrightarrow {{v_2}} \). Động lượng của hệ có giá trị là